Borehole survey means and core sample orienting means

ABSTRACT

MEANS ARE PROVIDED FOR DETERMINING THE HORIZONTAL DIRECTION (AZIMUTH) AND ANGLE FROM THE VERTICAL (INCLINATION) OF A BOREHOLE AT OR NEAR ITS BOTTOM. TO DO THIS A TUBE OF GELLABLE LIQUID AND A RESERVOIR OF A SECOND LIQUID WHICH CAN INITIATE GELLING OF THE FIRST LIQUID ARE ASSEMBLED AND LOWERED WITH THE DRILL STRING. THE LIQUIDS ARE SEPARATED BY A VALVE AND A MAGNETIC FLOAT FLOATS IN THE FIRST LIQUID. THE VALVE IS OPENED, WHEN REQUIRED, BY VARYING THE PRESSURE ON THE DRILLING LIQUID AND THE FIRST AND SECOND LIQUIDS ARE ALLOWED TO MIX. GELLING OCCURS AND THE MAGNETIC FLOAT IS &#34;FROZEN&#34; IN THE GEL. EXAMINATION OF THE FLOAT AND MENSIONS LATER ENABLE THE INCLINATION AND AZIMUTH OF THE HOLE TO BE DETERMINED. BY USING APPROPRIATE DATUM MARKS ON THE VARIOUS COMPONENTS, THE CORE STRATA CAN BE ORIENTED.

Nov. 9, 1971 J. B. ROBINSON 3,613,221

,BOREHOLE SURVEY MEANS AND CORE SAMPLE ORIENTATING MEANS Filed Jan 14. 1969 2 Sheets-Sheet 1 INVENTOR JOHN BRIAN ROBINSON Nov. 9', 1971 ROBINSON 3,618,221

BOREHOLE SURVEY MEANS AND CORE SAMPLE ORIENTATING MEANS Filed Jan. 14. 1969 2 Sheets-Sheet 2 fill/III fill/Ill rll L INVEN'IOR Q 9 JOHN BRIAN ROBINSON' United States Patent 3,618,221 BOREHOLE SURVEY MEANS AND CORE SAMPLE ORIENTIN G MEANS John Brian Robinson, Sutherland, New South Wales, Australia, assignor to Joint Coal Board, Sydney, New South Wales, Australia Filed Jan. 14, 1969, Ser. No. 791,060 Claims priority, application Australia, Jan. 19, 1968, 32,455/ 68 Int. Cl. E2111 47/02 US. Cl. 33--205.4 11 Claims ABSTRACT OF THE DISCLOSURE Means are provided for determining the horizontal direction (azimuth) and angle from the vertical (inclination) of a borehole at or near its bottom. To do this a tube of gella'ble liquid and a reservoir of a second liquid which can initiate gelling of the first liquid are assembled and lowered with the drill string. The liquids are separated by a valve and a magnetic float floats in the first liquid. The valve is opened, when required, by varying the pressure on the drilling liquid and the first and second liquids are allowed to mix. Gelling occurs and the magnetic float is frozen in the gel.

Examination of the float and meniscus later enable the inclination and azimuth of the hole to be determined.

By using appropriate datum marks on the various components, the core strata can be orientated.

This invention relates to borehole survey means and means for the orientation of core samples.

Existing equipment for these purposes suffers from one or more of the following disadvantages:

(1) It is elaborate and expensive and therefore costly to maintain and replace when lost in a bore.

(2) It can not be included in the drill rod string during drilling so separate instrument runs are necessary. This is costly in terms of time and labor, particularly in deep holes.

- (3) It is delicate and easily damaged in service.

(4) Depth of operation is limited.

(5) A time factor is involved due to:

(a) The inclusion of a clockwork mechanism in its construction.

(b) The time required for acid to etch a glass tube.

(c) The time requried for gelatine to cool and set.

(6) It can not be used in slim holes (less than 3" diameter).

(7) A special core barrel is required.

(8) A skilled technician is required.

(9) Chemicals such as hydrofluoric acid which are awkward to handle are used.

The object of the present invention is to provide bore hole survey means and means for the orientation of core samples which are substantially free from the above disadvantages.

The advantages of the present invention are:

(1) It is simple in design and cheap to manufacture.

(2) It can be included in the drill rod string while normal drilling proceeds.

(3) Only three minutes delay on bottom is required for operation of the instrument.

(4) It can be operated at will without reference to a time factor.

(5) It is robust and can be designed to operate at any depth.

(6) It can be used in slim holes.

(7) It can be adapted to other type drill rod strings such as wire line.

Patented Nov. 9, 1971 LIMITATIONS (1) In common with all devices employing a magnetic compass for direction finding the instrument will be astray in a strongly magnetic rock environment.

(2) The instrument is restricted in use to bores sunk below the horizontal.

For convenience the invention will be described and claimed with the components in their normal upright position as at the commencement of drilling.

In one general form the invention is bore hole survey means comprising a hollow cylinder adapted at its upper end to prevent substantially the escape of fluid from the upper end and having holes through its wall near its lower end to admit drilling fluid so that air may be trapped in the upper end of the cylinder, a gel tube adapted to hold a gellable liquid, a reservoir adapted to hold a second liquid adapted when mixed with the first liquid to initiate gelling of the first liquid, a passage connecting the gel tube and reservoir, a valve normally closing the passage and adapted on sudden reduction of the pressure on the trapped air to be opened to allow the second liquid to flow into the gel tube and mix with the first liquid.

A preferred form of the invention is shown in the drawings in which:

FIG. 1 shows the assembly from a piston rod cover downwards to a drill rod coupling;

FIG. 2 shows a gel tube, gelled liquid and frozen float displaced from a gel tube cover, and

FIG. 3 is a longitudinal section on line 33 of FIG. 1.

All parts, with the exception of the magnetic float are constructed of non-magnetic material, such as brass, aluminum :alloy and non-magnetic stainless steel.

The principal components are an instrument body 1, a cylinder 2, a piston 3, a piston rod 4, an injector 5, a nonreturn check valve 6, a gel tube 7, a magnetic float 8, a gel tube cover 9, a piston rod cover 10, an instrument mounting 11 and a drill rod coupling 12.

ASSEMBLY OF THE INSTRUMENT In the assembly of the instrument components, the piston 3 fits within the cylinder 2 with the piston rod 4 projecting through a gland 13 in the top of the cylinder. The clearance between 3 and 2 is about 1/100 inch. The piston rod cover 10 has a lower end which screws onto the top of the cylinder 2 tightening against a seal 24 to provide a watertight compartment for the end of the piston rod 4, projecting through the gland 13.

Attached to the underside of the piston 3 and colinear with the piston rod 4 is the injector 5, which passes through a gland 14 in the upper part of the instrument body 1, into an injection chamber 15. The lower end of the cylinder 2 screws into a counterbore in the upper part of the instrument body 1. Water holes 16 near the bottom of the cylinder 2 provide access to the inside of the cylinder.

Below the injection chamber 15, a non-return or check valve 6, comprising a ball 6', seat =6A and spring 613, screws into a counterbore in the base of the instrument body 1. A cap 6C has a metering orifice 6D on the base of the instrument body 1, the latter of which also includes a spigot 7A provided for reception theeron of the gel tube 7 which is held against a sealing ring 26 on the spigot. The gel tube 7 is marked with a datum line 17 (FIG. 2) which is aligned with a datum line 18 (FIG. 1) on the instrument body 1. A magnetic float 8 in the form of a spherical ball containing a magnetic system is free to move within the gel tube 7. A suitable form of floating magnet is a hollow plastic sphere in which a bar magnet 8A is mounted along a diameter, the shell being weighted by a weight located substantially below the centre line of the bar when the bar is horizontal. The gel tube 7 is enclosed and held in position by a watertight gel tube cover 9 which screws onto a second spigot 9A on the instrument body 1, which is concentric to the spigot 7A, and seats against the sealing ring 25.

The instrument, which in its operative position has the piston rod cover 10 uppermost, is housed in the instrument mounting 11 and is secured to it by two locating screws 19 which maintain the datum line 18 on the instrument body in register with the datum line (FIG. 1) on the instrument mounting 11. Holes 21 in the instrument mounting 11 provide a passage for drilling fluid passing through the annulus or chamber 24A in the centre of the drill rod string. The instrument mounting 11 is secured to the drill rod coupling 12 by two screws 23 which keep the instrument mounting datum line 20 in register with the datum line 22 (FIG. 1) on the drill rod coupling 12.

PREPARING INSTRUMENT FOR OPERATION The instrument body is removed from the instrument mounting 11 and the gel tube cover 9, the gel tube 7, the non-return valve 6 and the piston rod cover 10 are detached. The travel of the injector 5 is set by adjusting the length of the piston rod 4 projecting through the gland 13, the amount of stroke being commensurate with the amount of chemical reagent to be injected. A small handle (not shown), screwing into the end 4A of the piston rod 4 is used for this adjustment. The injection chamber 15 is filled with a solution of ammonium persulphate or other suitable initiator catalyst through the counterbore in the bottom of the instrument body 1 where the non-return valve 6 fits. When the injection chamber 15 is full, the non-return valve 6 is refitted and the outside of the instrument wiped clean. The gel tube 7 is partially filled with a solution of AM9 and DMAPN or other suitable activator catalyst and the magnetic float inserted to float just below the level of the liquid, free from the effects of surface tension. AM9 is a chemical grout marketed under that symbol by Cyanamid Australia Pty. Limited. It is a mixture of two organic monomers, acrylamide and N,N-methylenebisacrylamide in proportions which produce very stiff gels from dilute aqueous solutions when properly catalyzed. DMAPN is B-dimethylaminopropionitrile, an activator catalyst which maybe used to gel AM9.

The gel tube 7 is fitted to the instrument body 1 with its datum line 17 in register with the datum line 18 on the instrument body. The gel tube cover 9 is replaced on the instrument body 1 to hold the gel tube 7 in position and seal it in a watertight compartment.

The instrument body, now fully charged, is inserted in the instrument mounting 11, which is already attached to the drill rod coupling 12. Locating screws 19 secure it in its correct position. Finally the drill rod coupling 12 is screwed into a drill rod of non-magnetic material such as aluminum alloy.

When placing the drill rod, housing the instrument, in the drill rod string, it is desirable to place it as close as possible to the core barrel. It is necessary, however, to isolate the instrument from the magnetic influence of the steel core barrel by a 10 ft. length of non-magnetic drill rod. Similarly 10 ft. of non-magnetic drill rod is required to separate the instrument from the steel drill rods above it in the drill string. These considerations having received attention, normal drilling operations can proceed.

4 OPERATIONAL PROCEDURE During drilling operations drill fluid is pumped from the surface to the bottom of the hole via the annuli in the drill rods and the core barrel. Of the fluid which enters the drill rod containing the instrument, most passes through the holes 21 in the instrument mounting into the drill rod beneath. Some however, enters the holes 16 at the bottom of the cylinder 2 and passes between the piston 3 and the wall of the cylinder 2. With balanced pressure on either side the piston 3 remains in equilibrium until activated at the close of drilling. To achieve this activation for the purpose of obtaining oriented core the following technique is used:

(1) The drill rods are rotated slowly with neutral feed to remove torsion and are then left stationary in the hole.

(2) Downward pressure is exerted by the drill rig on the drill string to hold the core barrel hard on bottom.

(3) The surface pump is accelerated to build up pressure in the pump circuit to the instruments operational level, say 200 p.s.i. Air, trapped in the upper part of the cylinder 2 when the tools are inserted in the hole, is compressed by the drill fluids in the cylinder 2.

(4) A fast-action by-pass valve inserted in the pump delivery line is quickly opened to abruptly collapse the pressure in the pump circuit.

(5) The sudden removal of the loading force allows the air compressed in the upper part of the cylinder 2 to expand rapidly creating a series of impulses which travel through the fluid in the cylinder 2 to the piston 3 and, acting upon its upper surface, force it downwards.

(6) The downwards movement of the piston 3 causes the injector 5 to inject the initiator catalyst through the non-return valve 6 into the gel tube 7. Turbulence inside the gel tube 7 quickly subsides and the magnetic float 8 takes up a position influenced by the earths magnetic field.

(7) After a set time, governed by the respective proportions of the chemicals in the gel tube 7, say 3 minutes, gelation of the AM9 solution occurs. This fixes the positions taken up by the magnetic float 8 and the meniscus of the liquid in the gel tube 7.

(8) The drill tools are carefully raised off bottom, avoiding rotation until the core lifter has had an opportunity to tighten on the core and break it off.

(9) The drill rods are removed progressively in the normal fashion until the rod housing the instrument is reached. Before this rod is disconnected it is necessary to project the datum line 22 on the rod coupling 12 to the rod below and in turn to the bottom of the core barrel. A convenient and accurate method of projecting the datum line involves the use of a telescope pivoting about a horizontal axis, e.g. a theodolite, Dumpy level or telescopic alidade. In a vertical hole the telescope can be set up at any convenient point but in an angle hole the telescope is positioned so that the hole slopes towards it and the axis of the hole lies in the same vertical plane as the arc of the telescopes travel. With the telescope in position, the rod housing the instrument is hoisted as high as practicable and the telescope is elevated to sight on the datum line 22 on the drill rod coupling 12. When the vertical crosshair of the telescope is satisfactorily aligned with the datum line 22, the telescope is depressed to sight on the drill rod or core barrel exposed near ground level and a mark is scribed at the appropriate place. This procedure is repeated until the datum line is projected to the bottom of the core barrel.

(10) When the core barrel is removed from the hole the datum line projected to the bottom of the barrel is marked on the side of the core, if protruding from the barrel, or otherwise on the bottom face of the core from which it is later transferred. This mark is now in alignment with the datum line 17 on the gel tube 7 and core orientation is established by reference to the magnetic float S in the gel tube 7. Under conditions where difliculty may be encountered in matching individual pieces of core recovered in the barrel, scribing diamonds fitted in the core lifter adaptor may be used to mark the core as it enters the core tube.

The technique used to activate the instrument when it is being used only for bore hole survey is identical with that described for core orientation with the exception that no attention need be paid to datum lines. The inclination of the hole is read from the meniscus using a suitable protractor. The azimuth is obtained by measuring with a protractor the angle between a line through the high and low point of the meniscus and a line through the north and south poles of the magnetic float 8. This angle is converted to a compass bearing.

The instrument operation as outlined above refers to a normal core drill string. With suitable modifications it can be adapted to other types of drill string. In the case of wire line drilling, where the core barrel passes through the annulus in the center of the drill rods, it would be necessary to couple the instrument to the core barrel by a 10 ft. length of non-magnetic material. Fittings for the retrieval of the core barrel-instrument assembly would also need to be attached to the top of the instrument. Non-magnetic wire line drill rods 20 ft. in length would be inserted in the drill string behind the core barrel.

What I claim is:

1. Bore hole survey means comprising, in combination:

(a) a hollow cylinder with means at its upper end to prevent substantially the escape of fluid from the upper end, and having holes through its wall near its lower end to admit drilling fluid so that air may be trapped in the upper end of the cylinder;

(b) a gel tube adapted to hold a gellable liquid;

(c) reservoir means interconnecting said gel tube and said cylinder, including a reservoir adapted to hold a second liquid adapted when mixed with the first liquid to initiate gelling of the first liquid; 7

(d) a passage connecting the gel tube and reservoir;

and

(e) a valve normally closing the passage and adapted on sudden reduction of the pressure on the trapped air to be opened to allow the second liquid to flow into the gel tube and mix with the first liquid.

2. Bore hole survey means as defined in claim 1 wherein the gel tube is at least partly filled with the first liquid; the reservoir is at least partly filled with the second liquid; and further including magnetic float means at least partly immersed in the first liquid.

3. Bore hole survey means comprising, in combination:

(a) a hollow cylinder open at each end;

(b) a hollow piston rod cover having an upper and lower end, and which cover is closed at its upper end and open at its lower end, and detachably secured at its lower end in substantially fluid tight fashion to the upper end of the cylinder;

(c) a piston slidably mounted with a small annular clearance within the cylinder;

(cl) a piston rod secured at its lower end to the piston and extending upwardly into the piston rod cover;

(e) first sealing means substantially preventing the passage of fiuid between the cylinder and the piston rod cover;

(f) an instrument body having a passage open at each end formed through it, and having:

(1) a hollow upper end extension of the instrument body detachably secured to the lower end of the cylinder, and

(2) holes formed through the cylinder wall below the piston and above the extension;

(g) an injector secured to the underside of the piston and extending downwardly into the instrument body passage;

(h) second sealing means substantially preventing the passage of fluid between the instrument body passage and the cylinder past the injector;

(i) a gel tube adapted to hold a gellable liquid;

(j) a check valve in the lower end of the instrument body passage adapted to allow the passage of liquid from the instrument body passage outwards, but not in the reverse direction, and said gel tube which is closed at its lower end and open at its upper end;

(k) said gel tube being secured near its upper end to the lower end of the instrument body around the check valve in substantially fluid tight fashion; and

(1) adjacent ends of the injector and check valve being normally spaced apart by means forming an injection chamber within the instrument body passage and bounded by the passage walls, the second sealing means, the injector and the check valve.

4. Bore hole survey means as defined in claim 3 further including a hollow instrument mounting open at each end surrounding the gel tube, and secured at its upper end to the lower end of the instrument body; said instrument mounting at its lower end having means adaptable to be connected to one end of a drill rod coupling, and having drilling fluid passage holes formed through its wall above its connection of the coupling.

5. Bore hole survey means as defined in claim 3 wherein the gel tube is at least partly filled with a gellable liquid; the injection chamber is at least partly filled with a second liquid adapted when mixed with the first liquid to initiate gelling of the first liquid; and a magnetic float is at least partly immersed in the first liquid.

6. Bore hole survey means as defined in claim 4 wherein the gel tube is at least partly filled with a gellable liquid; the injection chamber is at least partly filled with a second liquid adapted when mixed with the first liquid to initiate gelling of the first liquid; and a magnetic float is at least partly immersed in the first liquid.

7. Bore hole survey means as defined in claim 4, further including a gel tube cover closed at its lower end and secured at its open upper end to the instrument body lower end, and said tube cover disposed between the gel tube and the instrument mounting.

8. Bore hole survey means as defined in claim 5 further including a gel tube cover closed at its lower end and secured at its open upper end to the instrument body lower end, and said tube cover disposed between the gel tube and the instrument mounting.

9. Bore hole survey means as defined in claim. 6, further including a gel tube cover closed at its lower end and secured at its open upper end to the instrument body lower end, and said tube cover disposed between the gel tube and the instrument mounting.

10. Bore hole survey means as defined in claim 4 wherein upright datum lines are marked respectively on the instrument body, the instrument mounting and on the gel tube, and the three parts so marked are retained relatively with the datum lines in substantially the same vertical plane.

11. Bore hole survey means as defined in claim. 10 wherein a further upright datum line is marked on the drill rod coupling, and the other datum marked parts when connected to said drill rod coupling have their respective datum lines in substantially the same vertical plane as that on said coupling.

References Cited UNITED STATES PATENTS 2,292,838 8/1942 Jones --44 LEONARD FORMAN, Primary Examiner S. L. STEPHAN, Assistant Examiner US. Cl. X.R. 175-45 

